Goji berries on a branch, dried in a bowl and steeped in a cup.

Goji Berries: Eye-Health Research, Portions and Warfarin

Posted on: Edited on: ~11 min read

What are goji berries?

Goji berries, or wolfberries, are the red fruits of Lycium plants in the nightshade family. Two species occur in Chinese food and medicinal traditions, Lycium barbarum and Lycium chinense. The dried fruit, a bottle of juice and a capsule of isolated fruit polysaccharides contain different mixtures of food and plant compounds.

People eat goji berries or take supplements for eye health, particularly to support the retina.

Two of those compounds explain much of the research interest. Zeaxanthin is a yellow-orange pigment found in the central retina. Polysaccharides are chains of sugars that researchers can extract from the fruit. If you take warfarin, discuss goji with your doctor before adding it. Reported bleeding and INR changes

How was goji used as food and medicine?

In Chinese medicine the dried fruit is called gou qi zi. Practitioners describe it in traditional terms as nourishing the liver and kidney and replenishing jing, or essence, for eyesight. An account of its culinary use describes dried berries cooked in soup or porridge and steeped in hot water. Traditional medicine monograph[1] · Wolfberry food preparations[2]

Which species did an older text mean? Researchers compared plants, herbals and regional records and found evidence that people used the two species interchangeably as food and medicine at least as far back as 682 CE. Cultivation of L. barbarum expanded in China from the 1960s. [3]

One famous longevity story concerns the herbalist Li Ching-yun. When he died in 1933, Time reported his own claim to be 197 and an even older age attributed to someone of the same name. The article itself questioned whether they were the same person. Its account mentions herbs and rice wine. [4]

Why do people take goji?

Claimed benefit Dose / form studied Research verdict Evidence strength
Increase pigment measured in the retina 28 g dried berries five times weekly for 90 days in healthy adults; another study used 25 g daily in adults with early macular degeneration In healthy adults, the berries showed no clear advantage over the comparison supplement. In early age-related macular degeneration (AMD), the 90-day pigment level was higher with berries than with usual diet. Eye studies Limited
Prevent macular degeneration or vision loss No established goji regimen These short studies did not establish lower risk of vision loss or late-stage disease. Insufficient
Reproduce food-trial effects with juice or capsules No established equivalent dose Extract weight alone cannot establish equivalence. Insufficient

Juice studies have also tested immune markers and how participants felt. A separate diabetes trial used an isolated fraction in capsules. Neither finding supplies a therapeutic portion of dried fruit.

What should you compare on the label?

Form What the amount describes What was actually tested
Dried whole berries Grams of fruit per serving, including its fiber Two eye studies used 25 g daily or 28 g five times a week. Dried fruit can also be a snack or an ingredient in oatmeal, soup or tea.
Juice Milliliters of a particular juice; check the ingredient list, serving size and added sugar Short studies tested 120 mL per day of one standardized product. The amount of polysaccharides, fiber or zeaxanthin in another juice may differ.
Milk-based wolfberry powder Grams of the complete formulation, including its milk ingredients Reports used 13.7 g daily and measured eye or vaccine-response outcomes.
Isolated polysaccharide capsule Milligrams of the extracted fraction A three-month diabetes study used 300 mg per day. This amount cannot be converted into grams of berries from the label alone.

Processing can change what reaches the blood. In a crossover experiment, 12 adults ate the same amount of zeaxanthin in three different wolfberry preparations with breakfast. The berries homogenized in hot skim milk produced a substantially larger blood response than the hot-water and warm-milk preparations. [5]

Pigment was higher than with usual diet in early macular degeneration

The macula is the central part of the retina used for detailed vision. It contains pigments including lutein and zeaxanthin that absorb some short-wavelength light. Macular pigment optical density estimates how much light this pigment absorbs. Researchers can measure a change in density months or years before they could establish whether a food changes the course of an eye disease.

Healthy middle-aged adults. A 2021 pilot assigned 31 adults aged 45 to 65 to 28 g of dried goji five times a week or a lutein/zeaxanthin supplement. Participants knew which they received. Twenty-eight finished, and researchers analyzed 27. After 90 days, the berry group’s pigment density had risen from baseline at two of four retinal locations. The change over time did not differ significantly between the two groups at any location. [6]

People with early age-related macular degeneration (AMD). A separate study assigned 114 people to 25 g of dried berries daily or their usual diet. At 90 days, average pigment density was higher in the berry group than in the usual-diet group. The researchers also reported that visual acuity improved from the berry group’s own starting point. They did not report a direct test of the difference in acuity change between groups. Neither study followed participants long enough to establish whether fewer people lost vision or progressed to advanced AMD. [7]

A trial of a milk-based wolfberry powder measured eye findings in healthy adults aged 65 to 70. A related report on the same type of preparation examined the response to flu vaccination. [8]

What do the juice and immune studies show?

In a 30-day trial, 60 healthy adults aged 55 to 72 received 120 mL daily of a branded wolfberry juice or placebo. Total lymphocytes, a group of immune cells, increased with juice, as did interleukin-2 and an antibody called IgG. Two specific types of T cell, CD4 and CD8, and natural killer cells showed no clear change. The lead author was affiliated with the company that sold the juice. [9]

Participants taking juice also reported changes in fatigue and sleep compared with their own starting scores. That does not show the immune changes caused them to feel better. A separate two-week parallel-group study reported improvements in self-rated energy, calmness and concentration within the juice group. [10]

A pooled analysis of four trials of the same 120 mL daily juice serving compared questionnaire responses from 161 participants. Self-rated focus, sleep quality and stress favored juice in the analysis that allowed effects to vary across trials. Depression and calmness ratings depended on the statistical method. This pools earlier juice studies rather than adding 161 new participants to the individual reports. [11]

A three-month report involving 150 older adults tested a milk-based wolfberry formulation and the immune response to flu vaccination. Flu-specific antibody levels and the proportion developing a defined antibody rise were higher with the formulation than with placebo. Other immune tests showed no clear advantage. The trial did not demonstrate that fewer participants caught influenza. This report and the eye report used the same product, age range, sample size and duration and share several authors. [12]

Meal-test glucose fell, while mood results depended on who rated them

A trial in adults with type 2 diabetes compared 300 mg daily of a wolfberry polysaccharide fraction with a cellulose placebo for three months. The study excluded people taking insulin. The paper describes 74 eligible adults and gives results for 67 who completed the study, 37 on the extract and 30 on placebo. All seven losses occurred in the control group. At the start and again after three months, researchers tracked blood glucose over several hours after a standardized meal. Compared with each group’s initial test, the total glucose measured across those hours fell about 7.9% with the extract and rose about 1.6% with placebo. The total insulin response did not clearly change. [13]

A separate six-week study tested a 300 mg daily polysaccharide tablet in adolescents with depressive symptoms below the threshold for major depression. An interim report on 29 participants found lower clinician-rated depression scores with the tablet than with placebo. The difference at six weeks was about three points on the 24-item Hamilton scale. Participants’ own depression ratings, anxiety, sleep and distress scores showed no clear group differences. [14]

Lab experiments help explain why these fractions draw interest. In a simulated digestive system, microbes from the human gut fermented wolfberry polysaccharides and produced short-chain fatty acids. In a separate experiment, researchers applied a wolfberry fraction to cultured rat nerve cells and found less injury after exposure to glutamate. Fermentation study[15] · Nerve-cell study[16]

What are the safety concerns?

Potential drawback When / who it affects Research evidence Practical implication
Excess anticoagulation or bleeding People taking warfarin who add concentrated goji tea, juice or wine Case reports[17] describe a raised INR, the blood test used to monitor warfarin, sometimes with bleeding. Consult your anticoagulation team before starting or stopping goji. Share the product, amount and date of use.
Severe food allergy People who react after eating goji Two cases[18] included one episode of anaphylaxis. Testing suggested that antibodies binding a goji protein could also recognize a tomato protein. Sharing a plant family does not tell us which foods an individual will react to. Avoid a food that has caused an allergic reaction and seek an allergy assessment. Breathing trouble or throat swelling after eating needs emergency care.
Undeclared sulfites People with sulfite sensitivity eating a specifically affected dried product In 2022, BCS International recalled Dr. Snack Goji Berry after New York inspectors detected undeclared sulfites. The FDA lists the recall as terminated. Check the ingredient statement and product-specific recall notices. [19]
Additional glucose effects People using diabetes drugs who are considering a concentrated extract The small capsule trial excluded insulin users and did not establish the risk of low glucose with individual diabetes drugs. Discuss the extract and usual glucose readings with the prescriber.
Delayed eye care Anyone with new or worsening visual symptoms The short studies measured pigment and did not establish that goji treats new vision loss. Arrange prompt assessment of new visual changes.

Why the warfarin reports matter

A woman who had been stable on warfarin developed an INR of 4.1 after four days of concentrated goji tea. In the laboratory, the tea only weakly inhibited an enzyme that helps break down warfarin. Another woman experienced two episodes of raised INR after drinking a tea containing goji. Those observations strengthen the reason for caution, while leaving the mechanism uncertain. Lam and colleagues[20] · Leung and colleagues[21]

A third patient was hospitalized with bruising, nosebleeds and rectal bleeding after four days of goji juice while taking warfarin. Her clotting test was too prolonged to give a numerical INR on presentation. A separate report describes visible blood in the urine after goji wine. That paper also followed three warfarin users who drank a particular goji tea for three days and stayed within their stated INR range. With so few people and different preparations, these reports cannot give an interaction rate or define a safe portion of dried berries. Juice case[17] · Wine case and short tea observation[22]

What product testing can tell you

Contaminant results also belong to the samples tested. A study of dried berries from plantations and supermarkets in Ningxia tested for six pesticides. Measured pesticide levels in the plantation samples were below the limits used by the investigators. These local measurements describe the samples tested. The named sulfite recall is a separate example of a labeling failure in a specific product. [23]

The bottom line

If you like goji berries, buy them as a food you enjoy. Compare dried berries by price and ingredients, as you would any other food product. The eye studies are interesting, but they do not show that goji prevents vision loss. An eye-health claim is not a good reason on its own to pay more for a bag of berries.

Juice and capsules are different products. Check what a full serving contains and what it costs before paying for immune, blood-sugar or “concentrated” claims. If you take warfarin, speak with your anticoagulation team before adding any goji product: reports describe raised clotting-test results and bleeding after some preparations.

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References

  1. Traditional medicine monograph ↩
  2. Wolfberry food preparations ↩
  3. Historical botanical investigation ↩
  4. Contemporary account, May 1933 ↩
  5. Human absorption study ↩
  6. Healthy-adult dried-berry trial ↩
  7. Early-AMD dried-berry trial ↩
  8. Milk-based wolfberry study ↩
  9. Amagase and colleagues ↩
  10. Two-week juice trial ↩
  11. Four-trial juice analysis ↩
  12. Vidal and colleagues ↩
  13. Polysaccharide trial in adults with diabetes ↩
  14. Adolescent trial ↩
  15. Fermentation study ↩
  16. Nerve-cell study ↩
  17. Case reports ↩
  18. Two cases ↩
  19. FDA recall record ↩
  20. Original warfarin case and laboratory comparison ↩
  21. Leung and colleagues ↩
  22. Wine case and short tea observation ↩
  23. Ningxia sampling study ↩